In the conventional four cycle, reciprocating, internal combustion engine, particularly on automotive vehicles, the engine typically is operating under substantially no load or light load much of the time. During such no load or light load conditions only a relatively small engine displacement is needed. It is only when the engine is under heavy load that higher engine displacement is required, such as when starting or accelerating the vehicle. However, these heavy load conditions dictate the engine displacement even when light load conditions are involved because the engine must have the capacity to handle the heavy load conditions satisfactorily.
Thus, there has existed the problem of improving the efficiency of such engines by automatically varying the engine displacement in accordance with the load on the engine, with the engine displacement being minimized under low load conditions and greatly increased under high load conditions.
My U.S. patent application Ser. No. 837,030, filed Sept. 2, 1977, discloses a novel arrangement in which the engine displacement is varied in accordance with the load by providing a spring acting between each engine piston and the crankshaft so as to provide a stiff coupling between them under engine idle or other substantially no load conditions and to provide a resiliently deformable coupling under heavy load which deforms in proportion to the load. The expansion of this spring is limited so that when expanded to the full extent permitted the spring is compressed with a force equal to the piston force required to compress the fuel mixture during the compression stroke for proper combustion when the engine is under substantially no load.